Means for maturing and stabilizing road structures



g s. E. FINLEY MEANS FOR MATURING AND STABILIZING ROAD STRUCTURES FiledJune 23, 1926 Patented Aug. 2,1927. UNITED j STATE;

PATENT OFFICE;

SAM EVERETT Fm, OF ATLANTA, GEQBGIA."

mnms ron ma'runme AND s'rammzme non) s'ria ue'runns;

Application filed June as, 1920. Serial in. 118,048.

The invention relates to a novel apparatus for maturing and stabilizingroad structures, including those made of mineral aggregate andbituminous binding material, which comprises means for subjectingthebody of the road structure to a series of zone, whereby voids betweenalternatively varying pressures progressively applied in adirectionsubstantially normal to the road surface and-in parallel mixed with theaggregate throughout the.

.of alternately varying peripheral face of each rib curved transroadstructure, fixing the aggregate as a consolidated mass enveloped andunited in a matrix of the binder; these operations and results beingeffected, preferably, by

having continuous s aced relation and eights, with the a novel type ofroller circumferential ribs in versely.

In the accompanying drawings,

Fig. 1 is a partial side elevation of a typical road roller having thenew form of roller element applied thereto.

Fig. 2 is a front elevation partly in section, of the roller element.

In constructing roadways and thelike, of mineral aggregate andbituminous hinder, the ultimate desideratum is to obtain a roadstructure in which the mineral aggregate elements are firmlyinterlocked, with the larger elements at the bottom and the smallerelements grading off toward the top surface of the road in which thefinest aggregate is disposed as the wearing surface, this densified andcompacted body of graded aggregate being firmly imbedded in a matrix ofbituminousbindeii SucliTroad structure is ideal, in that it issubstantially homogeneous and uniform throughout, is water andweatherproof, and, while it is sulficiently resilient to provide aperfect rolling surface for vehicular traflic, it is inherently stable,against the shoving, rollm and scouring effects of such traflic, analtogether approximates a condition of permanen ce and durabilityunderall conditions of use. All road engineers have striven to attam thesehlghly desirable characteri'sticsin finished roads and it has longbeenan estab-' lished canon of practice to cover the prepared subgrade of aroad bed with mineral aggregate varying in sizes from the largest to thesmallest from the bottom upward.

and then gregate cation of" the binding medium thereto; means of a heavyroller, usually with a compact the layer ofmineral agsmoothcylindricalsurface, or,;in some cases,

with an interrupted cylindrical surface;

either before or after the applisuch, for example, as would/be formed bya ser1es of independently mounted disks, or by a unitary cylinderhavingcircumferential ribs of uniform height spaced at intervalslaterally of the roller surface. These various types ofrollers, asheretofore employed; have proven ineffective, however, to produce a roadstructure in which all of the elements of the aggregate are compressedinto a dense, compacted, interlocked and substantially uniform mass, forthe reason that the pressure applied by the roller is normal to thesurface of the road,-so that' the movement of the aggregate'elements isdownward and in the direction of movement of the roller, due to theaction of the curved surface of the roller shoving elements of theaggregate near the top of the layer ahead of it.

The present invention is designed to effect a thorough kneadin elementsof the roa structure, during the compacting operation,

ment of the roller, so that the elementsare and rubbing of the byinitially causing a movement of the elements downwardly,-

firmly interlocked, the larger sizesof the aggregate being forced towardthe bottom and the smaller sizes being worked toward the top, afterwhich the compacted 'str'uc5 ture is subjected to maximum pressureapplied in parallel zones over the entire surface, thereby producing asubstantiallyv homogeneous"mass,

practically proofagainst relativecmovement in any direction. To producethese results, the preferred instrumentalityis that illustrated inthedrawin s,

the elements of which are in whichl represents the body of-the rollingelement of a power roller, which may have a weight of ten tons,

but which wei ht may bevvaried according .to the particu ar type of roadbeing constructed The peripheral surface of the roller element 1 isprovided with a series of circumferential ridges or ribs 2 and 3sepasurfaces of the ribs are [unifor'ml peripherally and transversely,as indicated rated by intervening spaces, these ribs or ridges, .whichshould be continuous, alteron the drawings by the surfaces 4 and 5. Itwill be seen,therefore, that any part of the contact area of the roller-1 is curved in every direction; that is to say, no straight line,however short, would contact this surface at morethan one point, withthe result that the material of the road surface, which is engaged bythese contact surfaces of the ribs, is subjected -to alternatingvarying. pressures in a direction substantially normal to the roadsurface and in parallel spaced zones and to simultaneously imposedoppositely disposed lateral pressures in each zone,

as well asto pressure imposed by the for-- ward rolling movement of thesurface of each rib. This efiects a distinct rubbing, kneadingandcompressing' action'upon all of the elements of the road structure toforce the latter into most intimate interlocking engagementwith aminimum of voids between the aggregate elements.

I The apparatus may be used elfectivel in preparing the mineralaggregate base 0 the road structure, after the latter is distributed onthe prepared s ubgrade, by operating the roller over the surface of theaggregate layer. During the initial movements of the roller, the higherribs 2 sink into the loose aggregate and force the latter downward andalso laterally and forwardly to a slight extent, by the maximum pressurerepresented by the entire weight on the roller, which is distribut- .edby the peripheral faces of the higher ribs 2. As the roller is movedback and forth over the surface of the aggregate, all'portions of theaggregate body are ultimately subjected to this maximum pressure andkneadin effect' of the ribs until the entire mass 0 the aggregate isultimately consolidated and compacted, with the larger elements of theaggregate worked to the bottom and the smaller elements forced towardthe top, so

that, when the rolling operation iscomi "pleted, all *of'theelem'entsi'of the' aggregate applied, usually in the form of asphalt ofbitumen of any suitable character, andfinally a top dressing of stonechips, sand or the like, is spread over the surface, which is againsubjected to a thorough .rolling by the same roller, which has theeffect of kneading the binding material into the in terstices of themineral'aggregate layer" and 'compacting the surface 0 the roadway intoa dense and uniform wear resisting consistencyythat is impossible ofattainment with the older types of rollers.

It is to be noted that the act-ion of this particular type of roller isdistinctly "novel and the results obtained thereby are not approximatedby the rollers heretofore employed for this general purpose. On firstpassing over the more or less loose or uncompacted aggregate, the ribsof the roller sink in the loose aggregate until all of the peripheralsurfaces of the roller are in contact with the top surface of theaggregate and the pressure per square inch imposed by the roller is theleast possible. The material of the aggregate is rubbed and massaged,due to the divergent diameters of the and forced into the closestpossible contact.

ribs, kneaded and pushed in all directions" All bridging of theaggregate is prevented,

the fine material is rubbed into the voids and the coarse non-friablematerial is forced deeper into the surface, while the finer;

contact represented by the engaging peripheral surfaces of the higherribs 2, thereby producing a maximum pressure on the road structure atthese points of contact, and, as the rollingoperation is continued untilthe entire road surface has been treated, it is. apparent that the wholearea of the road will ultimately be subjected to the maximum pressurerepresented by the entire weight of the roller, as distributed by theengagementthereof by the higher" ribs. A ten ton, roller of the usualcylindrical type ordinarily weighs about two hundred pounds per linearinch of roll. If the areaof contact of such a roller were less, as inthe ribbed type con- .i stituting the present invention, the pressureper square inch upon the road structure would be increased indefinitelyand limited only by the moduli of elasticity of the materials incontact.

' Many road and street surfaces of the mineral aggre ate asphalt bindertype require long perio s in which to mature and to reach their besteffectiveness. This matgri ng f process is aided by the action oftrafiic; which I dition.

performs slowly and in lanes some of the functions which the instantinvention produces quickly and uniformly over the full surface of theroad. For example, asphalt macadam is usually compacted with a rollerweighing approximately two hundred pounds per linear inch of roll and isfinished by casting dry stone chips over this surface. Traific is thenturned on and the dry stone gradually imbedded or worn away, while theasphalt and fine material is kneadedto the surface. This maturing bytraflic occurs first in traflic lanes, while outside of these lanes thematuring is very slow. In anyca'se, ay'ear or more is usually requiredto bring the roadway to its best con- The machine heretofore described,and the method which it carries out, are designed to greatly acceleratethe 'maturing process, while, at the same time, conserving the mineralaggregate and not wasting it in dust produced by the attrition ofvehicle wheels. The same rapid maturing and stabilization isaccomplished by the use of this method of machine on various other typesof road construction. Among these may be included, all road ty es,depending upon a binding medium whic is'lfquid or a combination ofliquids, whether these types be hot mix pavements, or those manufacturedby. the application ofbituminous or other binding medium by penetrationprocesses. In the hot mix types, the kneading, working and imbeddingprocess, in combination with large finshing pressure per square mch,produces the most compact and most densemixture possible. Further, itdecreases the perviousness to a minimum and increases the supportingpower and stability of the road structure to a maximum. In thepenetration types, mutually soluble combinations of liqu1d.bitumens maybe used and the elimination of the less viscous bitumen is hastened bythe mechanical action of the oxidation, and the more rapid release ofthe lighter molecules, carrying with them entrained heavy molecules,together with the working into the matrix of the more finely dividedaggregate. Also, emulsions of bitumen in water are quickly broken underthis roller, releasing the water and coalescing the elements of thebitumen. It will be seen, therefore, that the method herei'nbeforedescribed and the apparatus by means of which the same is carried out,are most effective not only in preparing and compacting foundations ofmineral aggregate, but are also particularly eflicacious in rapidlymaturing and stabilizing the wearing surfaces of bituminous concreteroadways.

While the invention has been described with particular reference to itsapplication in treating bituminous concrete road structures, it is to beunderstood that it is not limited to this specific type of road, butevidences a high degree of utility in maturing and stabilizing roadstructures of clay,

gravel, sand, earth, water-bound macadam and other types.

What I claim is: 1. Means for maturing and stabilizing.

composite road structures, comprising a roller having continuouscircumferential ribs in s aced relation and alternatel varying heig tson its periphery,'the perip eral face of each rib belngcurvedtransversely.

2. Means for maturing and stabilizing composite road structures,comprising a roller havin continuous circumferential ribs in s acerelation and alternately var in heig ts on its periphery.

I testimony whereof I afiix'm si ature. SAM EVERETT I EY.

